This invention relates to a medical instrument.
The usefulness of obtaining a complete record of foetal heart rate during delivery is now recognised extensively in the Western world. Sometimes it is used routinely and becomes part of the general birth record and more significantly it is used with babies at risk. By linking the heart rate with contractions and cervical dilatation etc., an obstetrician has an early warning of fetal distress and is then well placed to deal with it at the outset. The first successful device took the form of an insulated suture clip which could be attached to the fetal head and complete an electrical circuit with a second electrode in contact with the mother.
Later modifications of such a device included at the leading end a helical electrode which was attached to the foetal scalp by rotation of an applicator, this motion being transferred to the electrode causing it to advance helically. A double helix has also been used at the leading end for a uniform approach to the fetal scalp. However, a problem with such previously-proposed devices was that over-rotation of the helical electrode could traumatise the fetal scalp or bend the electrode beneath the surface, making removal difficult. Damage could thus be caused to the foetus.